CF341A

题目连接

http://codeforces.com/contest/621/problem/A

Description

Today, Wet Shark is given n integers. Using any of these integers no more than once, Wet Shark wants to get maximum possible even (divisible by 2) sum. Please, calculate this value for Wet Shark.

Note, that if Wet Shark uses no integers from the n integers, the sum is an even integer 0.

Input

The first line of the input contains one integer, n (1 ≤ n ≤ 100 000). The next line contains n space separated integers given to Wet Shark. Each of these integers is in range from 1 to 109, inclusive.

Ouput

Print the maximum possible even sum that can be obtained if we use some of the given integers.

Sample Input

3
1 2 3

Sample Output

6

题意

给出一组数，找出其中最大的偶数之和

题解

奇+奇=偶 偶+奇=奇 偶+偶=偶 ，如果总和是奇数，那么N个数之中一定有一个数是奇数，由偶+奇=奇知 奇-奇=偶 奇数总和减去最小的奇数得到最大的偶数和。

代码

#include<bits/stdc++.h> using namespace std;const int INF = 1e9+7;int main(){    long long n,sum=0,single=INF;    scanf("%I64d",&n);    for (int i = 0; i < n; ++i)    {        long long t,ok=0;        scanf("%I64d",&t);        sum+=t;        if (t%2!=0){            single=min(t,single);        }    }    if (sum%2!=0)    {        sum-=single;    }    printf("%I64d\n",sum );    return 0;}

注意

• long long与int不要混用，long long->I64d，int->d。不要混搭
• const int INF = 1e9+7 控制大小
• 且long long不要用ld输入。